The present invention relates to a liquid crystal display device.
In a related-art liquid crystal display device such as liquid crystal television, a light guide plate is disposed behind a liquid crystal panel, a plurality of light emitting elements such as LEDs are provided around the light guide plate as a light source, and light emitted from the light source is used as backlight that is incident on the liquid crystal panel through the light guide plate. When all of the light emitting elements disposed in the light source are turned on all the time, image blur (image sticking) occurs in a display screen. Accordingly, the driving timing of the liquid crystal panel is adjusted to turn off the light emitting elements each time an image signal of one frame is input to the liquid crystal display device, thereby displaying a black screen. This signal processing is called black insertion driving process. In the black insertion driving process, the amount of current or voltage applied to each light emitting element is sequentially controlled to switch the light emitting elements to be turned on or off, as required.
However, the above process that sequentially controls the amount of current or the voltage applied to each light emitting element is not efficient because a large process load is applied to a control unit such as a CPU.
Therefore, for example, Japanese Patent Publication No. 2005-302712 A discloses an LED driving circuit which includes a series-parallel circuit in which a plurality of parallel circuit blanches which are connected in series to each other and each of the parallel circuit blanches includes one or more LEDs (light emitting elements) and at least one switches which are connected in series to each other.
According to the LED driving circuit disclosed in Japanese Patent Publication No. 2005-302712 A, a plurality of series circuits in which LEDs for each color and switches are connected in series to each other are connected in parallel to each other. Therefore, when an arbitrary switch is turned on, a potential difference occurs only in the LED for an arbitrary color, connected to the switch to turn on the LED. Accordingly, it is possible to prevent a variation in the display color or the brightness of light emitted from the LED on the display screen.
In the liquid crystal display device including the LED driving circuit disclosed in Japanese Patent Publication No. 2005-302712 A, it is possible to easily prevent the variation in the display color or the brightness of light on the display screen without sequentially controlling the amount of current or voltage applied to each light emitting element. Japanese Patent Publication No. 2005-302712 A, however, does not disclose a detailed method of switching the light emitting elements to be turned on or off according to the driving timing of the liquid crystal panel in, for example, the black insertion driving process.